Anodized silicon-manganese aluminum base architectural alloy

ABSTRACT

AN ALUMINUM BASE ALLOY CONTAINING IN PERCENT BY WEIGHT 3.5-6.5 SILICON, 0.3-0.65 MANGANESE, 0.1-0.7 IRON, A MAXIMUM OR 0.3 COPPER, A MAXIMUM OF 0.1 MAGNESIUM, ABD A MAXIMUM OR 0.1 TITANIUM, WITH A MAXIMUM TOTAL OF OTHER ELEMENTS 0.15%, AND NO MORE THAN 0.05% OF ANY ONE OF THESE OTHER ELEMENTS. THIS ALLOY IS COLORABLE BY ANODIZATION TO AN ATTRACTIVE SLATE-GRAY.

"United States Patent Ofice 3,790,452 Patented Feb. 5, 1974 3,790,452 ANODIZED SILICON-MANGANESE ALUMINUM BASE ARCHITECTURAL ALLOY William A. Anderson and"Edn1und C. Franz, Pittsburgh,

Pia, assignors to Aluminum Company of America,

' Pittsburgh, Pa.

No Drawing. Original application Dec. 17, 1969, Ser. No. 886,010. Divided and this application Feb. 3, 1972, Ser. No. 223,379

Int. Cl. C23b 9/02 U.S. Cl. 204-29 7 Claims ABSTRACT OF THE DISCLOSURE An aluminum base alloy containing in percent by weight 3.5-6.5 silicon, 0.3-0.65 manganese, 0.1-0.7 iron, a maximum of 0.3 copper, a maximum of 0.1 magnesium, and a maximum of 0.1 titanium, with a maximum total of other elements 0.15%, and no more than 0.05% of any one of these other elements. This alloy is colorable by anodization to an attractive slate-gray.

This is a division of application Ser. No. 886,010, filed Dec. 17, 1969, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to an architectural alloy anodizable to an attractive slat-gray color. More particularly, it relates to an aluminum base alloy containing silicon, manganese and iron, with or without a small amount of copper.

Aluminum base alloys are known which give a relatively dark gray or black shade on anodizing. For example, the aluminum-silicon alloy designated by the Aluminum Association as 4043 is colorable to dark grayby anodizing in a conventional sulfuric acid electrolyte. This alloy contains 4.5 to 6.0% silicon, a maximum of about 0.8% by weight iron, up to about 0.3% copper, a maximum of 0.05% for each of manganese and magnesium, about 0.2% titanium, and 0.1% zinc. Alloy 3003 also gives a dark gray color upon anodization under controlled conditions in certain organic acid type electrolytes. This alloy contains 1.0-1.5% manganese, 0.05-0.20% copper and up to 0.6% silicon, 0.7% iron and 0.1% 'zinc. Another alloy which also gives a dark gray to black color upon anodization in certain organic acid type electrolytes is 6351, an aluminum base alloy, containing 0.7 to 1.3% silicon, about 0.5% iron, 0.15 to 0.4% copper, 0.4% to 1% manganese, and 0.5% to 1.2% magnesium.

To achieve the desired color response with these alloys requires especially careful controls On homogenization and cooling of the ingots and their fabrication tosheet. Even so, the alloys sometimes develop a streaked condition during anodization, particularly with an undesirable yellow color component, and each' requires a specific electrolyte to develop a gray shade. Therefore, development of an architectural alloy which is anodizable to an attractive slate-gray color of a substantially unstreaked even texture, and has the additional advantage of developing such color by anodizing in conventional electrolytes, represents a highly desirable result.

SUMMARY OF THE INVENTION It is accordingly one object of this invention to develop an architectural alloy capable of achieving a pleasing slate-gray color when anodized. Another object of this invention is to develop a method of producing an aluminum base alloy colorable to a substantially non-streaked pleasant slate-gray color when used for architectural purposes. A further object is to develop an aluminum base alloy capable of becoming slate-gray upon anodization in conventional electrolytes. Other objects will be apparent hereinafter from the description and claims which follow.

In its broader aspects our invention involves an architecutral alloy having as essential ingredients thereof from about 3.5 to about 6.5% by Weight silicon, from about 0.3 to about 0.65% by weight manganese, from about 0.1to about 0.7% by weight iron, up to about 0.3% by weight copper, up to about 0.1% by weight titanium as a grain refining element, and up to about 0.1% by weight magnesium. Other elements in the form of impurities may amount to about 0.15% by weight, but there should be no more than 0.05 by Weight of each.

According to our invention, the alloy, after casting, is homogenized by preheating and preferably worked by hot rolling to a desirable sheet thickness, and, if a thinner sheet is desired, by cold rolling following the hot rolling. To develop the desirable substantially unstreaked and uniform slate-gray color, the alloy is anodized by com ventional procedures, for example, by anodization in a sulfuric acid electrolyte, in a sulfophthalic acid (SPA) type of electrolyte, or in other known anodizing electrolytes. The alloy may be clad on another aluminum base alloy, for example 3003, if desired.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples are illustrative of our invention.

Example 1 Several ingots of the alloy composition of the invention (specific amounts of elemental components given below) 16" x 50" x were cast. These were fabricated into sheet gages, including 0.167-inch hot-line sheet, and cold rolled from that gage to 0.125-inch and 0.080-inch thicknesses. Before the aforementioned hot and cold rolling, the ingots were preheated and scalped, the preheating being at about 1050" F. The preferable preheating temperature is 990-l050 F. Several ingots were fabricated into clad sheet by cladding the alloy composition of the invention onto a 3003 alloy. Cast ingots of prior art alloys were similarly rolled and fabricated for comparison with the alloy of this invention for development 'of color upon anodization. The following table (Table I) gives the composition of two examples of a prior art alloy and the composition of two examples of the present invention.

TABLE I.-CAST ANALYSES The specific fabrication procedures for the sheet and clad sheet material of the prior art and for the alloy of this invention were as follows:

Prior art Alloys A and B:

0.08 -inch thick sheet and trea anodizing procedues.

24 a.s.f., 80 F., 20 min., 15 min. boiling water seal 24 a.s.f., 85 F., 20 min., 15 min. boiling water seal grelheat practice ihours at1,000 F. 9 -fl, 90 F-, 60 min., 15 min. boiling water seal 08 p o o filgfitdljeheit 1 hour at 950 F. Uniform slate-gray colors were developed m all 1n- 0 1'60 Alloys A and B of this invention: stances gre heat practice 0 hours at 990 F. Example 3 ca 1 r t oho m 1 hour nt950 F. SIX panels of the Alloys A and B of Table I of Ex- 3,. fifg g'gga' mgggggw g y 1 ample 1 f bricated substantially according to the process P i r ot 4h 10F v of Examples 1 and 2 except where otherwise indicated i 9 at f: m Table III, which'follow s,. were anodized for-"60 minutes cl ag r o rg ag y both sides 013003 as r at 9 a.s.f. and at 90 in an electrolytecontaining 96,8 rn 'o reh 11mm M9100 F 15 8 SPA a d 5 g-/l. H280 These samples 'were giv 11 a Roll direct -minute boiling water seal and desmudged'with pumice A r before reflectance measurements were made- Table III 13 4 hours t F- shows reflectance results for: both clad and nonclad o griag'gi'aigjai gx'ga'ietrSlat;at 20 y 8S X X S8 I Ingot reheat 1 hour at 910 'F. TABLE III Roll direct Yellow- AfPparent ness All of the precedmg sheet samples were anodized 1n i i 18ml an electrolyte made up of 100 g./l. SPA and 5.5 g./l. Pri rartA11 yA(n n- 1ad)l m1 0'5 H 80 under the conditions shown in the following table 2 Big fi gg gggfig mzkh -4 (Table H). Coatings approximately 0.7 mil in thickness 11110;]; ofthisinvention clad to3003 12.4 were formed. Values for apparent reflectance and yellow- A "mils invention =1461 4 3 A110 B otthisin ti lad ness factor as recorded in Table II and following tables y y 9 (nonc 14 E 1 Solution heat treated and air bliut quenched. were determmd i a modlfiqd color val-gen of 1 Solution heat treated and cold water quenched. the photoelectric tristlmulus colonmeter described in US, V National Bureau of Standards Circular No. C429 by R. S. 3 Hunter substantially according to the procedure described The slate-gray color developed for the alloy of the inin US. Pats. 3,098,724 and 3,379,580. stant invention, as shown by the reflectance values. in the TABLE II Voltage 1 i Yellow-- A parent ness Gage (inch) Alloy Initial Final re ectance (actor 9 a.s.l'., 90 11,55 min.

0.167 Prior art Alloy A -7 2s 9.1 I 2.9 0.167.... AlloyAof this invention (clad).... 25 '44 12.4 1.1 0.167 Alloy A of this invention (non-clad) 28 40 11. 2 2. 2 0.125.- Prior art Alloy B 28 40 8.7 I 2.8 0.125-- Alloy B of this invention (clad). 25 44 12.9 7 0.125.... Alloy B of this invention (non-clad)... 28 40 12.4- 4. 1

24 51.3.1 F., 20min 0.107.....': Prior art Alloy A 39 4. 0 1.4 0.167-... Alloy A of this invention (clad)-... 35 97 0. 3 l 5 0.167.... Alloy A of this invention (non-clad) 35 89 0. 4 -3. 2 0.125 Prior art Alloy B 31 95 4. 7 2. 4 0.125... Alloy B of this invention (clad) 35 97 0.4 1.9 0.125 Alloy B of this invention (non-clad) 35 8e 0.0 --.2.9

' "9 8.51..70 F., co min. i

0.167 Prior art Alloy A r 33 53 5. 8 -1 8 0.167.... Alloy A of this invention (clad) 28 58 7. 0 4 7 0.167--.. Alloy A of this Inventiou (non-clad) 28 80 0. 4 3. 1 0.125.-.- Prior art Alloy B 33 5:1 5. 6 1.8 0.125---. Alloy B of this invention (clad) 28 58 7. 4 -2;1 0.125 Alloy B of this invention (non-clad) i 28 80 '0. 2 -0. 5

I 24 a.s.l., 70 F., 20 min.

0.107 Prior art Alloy A as 10 4.2 1-0.5 0.107-- Alloy A of this invention (clad) 35 88 5.8 2. 3 0.167-. Alloy A of this invention (non-clad)... 83 90 0. 5} 3. 5 0.125-... Prior art Alloy B 38 4.4 I 1.7 0.125.... Alloy B of this invention (clad)-. 35 g8 5 9 ..-2 5 0.125 Alloy B of this invention (non-clad). I 33 90 5, 7 3

l Amperes per sq. ft. V v v I j The 90 F. treatment of the preceding tablep'roduced foregoing table, tended towards a gray coloration similar a somewhat lighter slate gray than an 85 F; treatment 65 to that of the prior art samples, but exhibited an for Alloys A and B of this invention. Prior Art Alloys A essentially streak-free appearance in'contrast to an oband B e b t an y 0r streaked-gray pp ara iectionable degree'iof structural streaking' shown by the in contrast to the attractive slate gray exhibited by the prior art alloys. r Alloys A and B of this invention. 7 Example 4 Three sheet products of an alloy of substantially tlie same composition as Alloy A of this invention of Table 1 of Example 1 were produced in the same manner as that indicated in Example 1 except for being rolleddown to 75 weight'of the "elemental components,

16" x 50" x ingot was cast and fabricated-substantially according to the procedure. of Example 1 to a 0.125" thickness and into sheet section s"60" wide by 12' long. alloy had the following' analysis in percent'by Samples of this product were treated with the anodizing electrolyte of Example 3 with the following results as to color and reflectance:

Apparent ness Anodizing procedure reflectance factor 9 a.s.f. at 90 F. for 60 min 11.8 5. 3 12 a.s.f. at 85 F. for 45 min 7. 8 2. 7 24 a.s.f. at 80 F. for 25 min 6. 2 -0.4

Samples of the same product were also treated in 16% by weight of H 80, with the following results as to color and reflectance:

Coating thick- Yellowness, Apparent ness Anodizing procedure (mils) reflectance factor 24 a.s.f. at 75 F. for 23 rnin 0.7 16.6 2.9 24 a.s.f. at 75 F. for 26.4 min 0.8 15. 4 -0. 2 24 a.s.i. at 75 F. for 29.2 min 0. 9 13. 3 0. 24 a.s.f. at 75 F. for 33.0 min- 1. 0 11.2 -0. 4 24 a.s.f. at 75 F. for 36.3 min 1. 1 10. 9 1. 1

From the above results, it can readily be seen that use of the architectural alloy of our invention produces an improved attractive slate-gray color.

While the invention has been described in terms of certain preferred embodiments, the claims appended hereto are intended to encompass all embodiments which fall within the spirit of the invention. Having thus described our invention and certain preferred embodiments thereof, we claim:

1. A process for production of a substantially unstreaked slate-gray color on a wrought aluminum base alloy sheet which comprises anodizing said alloy sheet in an electrolyte capable of forming said color, said alloy consisting essentially of from about 3.5% to about 6.5% by weight silicon, from about 0.3% to about 0.65% manganese, from about 0.1 to about 0.7% by weight iron, up to about 0.1% by weight magnesium, up to about 0.3% by weight copper, and up to about 0.1% by weight titanium, the balance being essentially aluminum except for about 0.15% by weight other elements and no more than about 0.05% by weight of each of said other elements.

2. A process for production of a colored architectural aluminum base alloy sheet which comprises casting an aluminum base alloy consisting essentially of from about 3.5 to about 6.5 by weight silicon, from about 0.3% to about 0.65% manganese, from about 0.1% to about 0.7% by weight iron, up to about 0.1% by weight magnesium, up to about 0.3% by weight copper, and up to about 0.1% by weight titanium, the balance being essentially aluminum except for up to about 0.15% by weight other elements and no more than 0.05% by weight of each of said elements, homogenizing said alloy by preheating at 990-l050 F., rolling said alloy to sheet thickness, and anodizing in a sulfuric acid/sulfophthalic acid electrolyte for a sufficient length of time to develop a substantially unstreaked slate-gray color on said alloy.

3. A process for production of a substantially unstreaked slate-gray color on an aluminum base alloy which comprises providing an aluminum base alloy consisting essentially of from about 3.5% to about 6.5% by Weight silicon, from about 0.3% to about 0.65% manganese, from about 0.1 to about 0.7% by weight iron, up to about 0.1% by weight magnesium, up to about 0.3% by weight copper, and up to about 0.1% by weight titanium, the balance being essentially aluminum except for about 0.15% by weight other elements and no more than about 0.05 by Weight of each of said other elements, Working said alloy and thereafter anodizing same to said substantially unstreaked slate-gray color in an anodizing electrolyte selected from the group consisting of sulfuric acid and a mixture of sulfonic acid and sulfuric acid.

4. The process of claim 3 wherein the alloy is worked by rolling to sheet thickness.

5. The process of claim 3 wherein the anodizing is performed in a sulfuric sulfophthalic acid electrolytic bath at a temperature of from 80-90 F.

6. The process of claim 3 wherein the alloy provided forms a cladding on another aluminum base alloy.

7. A Wrought anodized aluminum base alloy article having an anodic coating thereon characterized by a substantially unstreaked slate-gray appearance, said alloy consisting essentially of from about 3.5 to about 6.5 by weight silicon, from about 0.3% to about 0.65% manganese, from about 0.1% to about 0.7% by weight iron, up to about 0.1% by weight magnesium, up to about 0.3% by weight copper, and up to about 0.1% by Weight titanium, the balance being essentially aluminum except for about 0.15 by weight other elements and no more than about 0.5% by weight of each of said other elements.

References Cited UNITED STATES PATENTS 1,595,218 8/1926 Pacz l48 2,993,784 7/1961 Huddle et al. 75148 3,128,176 4/1964 Martin 75-148 OTHER REFERENCES The Surface Treatment and Finishing of Al, by S. Wernick et al., 1964, pp. 298-303, 306-307, 747, 750.

JOHN H. MACK, Primary Examiner R. L. ANDREWS, Assistant Examiner US. Cl. X.R. 20458 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,790,452 Dated February 5, 1974 Inventor(s) William A. Anderson et a1 It is certified that error appears in'the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 28 After "attractive" change "slat-gray" to --slate-gray--.

Col. 2, lines 9 & 10 After "an" change "architecutral" to '--architectural.

Table II, Section 3, After "this" change "Inventiou" line 3 to invention-w Colo line 71 Before "16" insert -A-.

Claim 7, line 11 After "about" change "0.5%" to Signed and sealed this 22nd day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. 7 C. MARSHALL DANN Attesting Officer Commissioner of Patents F ORM PO-1OSO (10-69) USCOMM-DC 60376-P69 w u.s. GOVERNMENT rnm'rms OFFICE: 1969 0-366-331. 

